Shelf



FIG. 1 is a perspective view of a shelf showing my new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a front elevational view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a bottom view thereof; and,

FIG. 6 is a left end view thereof, the opposite end being a mirror image of the end shown. 

The ornamental design for a shelf, as shown and described. 